1. Field of the Invention
The present invention relates generally to jet aircraft turbine engines and, more specifically, to a noise reduction kit for retrofit on an existing engine and airframe.
2. Description of the Related Art
In view of noise restrictions placed upon the use of aircraft in certain areas and at certain times, a need has existed and continues to exist for quiet aircraft engines. There is a significant need for a method to modify conventional engines on aircraft that presently are in service, since aircraft with such engines often cannot be used economically, because of noise restrictions.
The prior art contains many instances of structure adapted specifically for retrofit or original fit on a jet turbine engine to suppress engine noise. Typically, the noise suppression structure consists of sound-attenuating liners applied to the nose cowl, the nose dome, and the fan duct components of the engine. Examples of such installations are shown in U.S. Pat. Nos. 4,751,979; 4,723,626 and 4,443,751. The installation of past prior noise suppression structures and devices in a retrofit application is extremely time consuming and detailed. The past systems also often require significant preventive maintenance to maintain the beneficial effects of noise suppression.
In applicants' view, the past efforts to design or retrofit aircraft engines to suppress noise levels have not been fully acceptable or successful. Many of the past designs and retrofits simply have not provided a meaningful noise reduction. Moreover, these past designs and retrofits have often been prohibitively expensive.